Thinking About a Megadungeon

I'm not a big fan of Grognardia, but eventually I found Maliszewski's Dwimmermourt campaign pretty appealing. It is, in a sense, proof that you can successfully run a D&D campaign lasting two years, starting from nothing more than a rough wilderness sketch and a fistful of levels. I am, on the other hand, a big fan of The Warlock's Home Brew and Beyond the Black Gate, both great blogs and cool campaigns. However, I also hold Henchman Abuse and his really cool megadungeon campaign in high esteem. So, here is what I thought: how about a pretty small-scaled map which features a couple of hot spots (no more than 5 or thereabouts) and only a big megadungeon, full of über-cool stuff but pretty isolated from the land above?

Don't get me wrong, I know this is not really an original idea, but I would like to work with something like this. Sounds like very little preparation combined with tons of fun. And I wonder if Geoffrey will ever release his infamous Carcosa megadungeon...